/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.entity.mime;

import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.content.AbstractContentBody;
import org.apache.http.entity.mime.content.ContentBody;
import org.apache.http.util.Args;
import org.apache.http.util.Asserts;

import java.util.List;

/**
 * Builder for individual {@link FormBodyPart}s.
 *
 * @since 4.4
 */
public class FormBodyPartBuilder {

  private String name;
  private ContentBody body;
  private final Header header;

  public static FormBodyPartBuilder create(final String name, final ContentBody body) {
    return new FormBodyPartBuilder(name, body);
  }

  public static FormBodyPartBuilder create() {
    return new FormBodyPartBuilder();
  }

  FormBodyPartBuilder(final String name, final ContentBody body) {
    this();
    this.name = name;
    this.body = body;
  }

  FormBodyPartBuilder() {
    this.header = new Header();
  }

  public FormBodyPartBuilder setName(final String name) {
    this.name = name;
    return this;
  }

  public FormBodyPartBuilder setBody(final ContentBody body) {
    this.body = body;
    return this;
  }

  public FormBodyPartBuilder addField(final String name, final String value) {
    Args.notNull(name, "Field name");
    this.header.addField(new MinimalField(name, value));
    return this;
  }

  public FormBodyPartBuilder setField(final String name, final String value) {
    Args.notNull(name, "Field name");
    this.header.setField(new MinimalField(name, value));
    return this;
  }

  public FormBodyPartBuilder removeFields(final String name) {
    Args.notNull(name, "Field name");
    this.header.removeFields(name);
    return this;
  }

  public FormBodyPart build() {
    Asserts.notBlank(this.name, "Name");
    Asserts.notNull(this.body, "Content body");
    final Header headerCopy = new Header();
    final List<MinimalField> fields = this.header.getFields();
    for (final MinimalField field : fields) {
      headerCopy.addField(field);
    }
    if (headerCopy.getField(MIME.CONTENT_DISPOSITION) == null) {
      final StringBuilder buffer = new StringBuilder();
      buffer.append("form-data; name=\"");
      buffer.append(encodeForHeader(this.name));
      buffer.append("\"");
      if (this.body.getFilename() != null) {
        buffer.append("; filename=\"");
        buffer.append(encodeForHeader(this.body.getFilename()));
        buffer.append("\"");
      }
      headerCopy.addField(new MinimalField(MIME.CONTENT_DISPOSITION, buffer.toString()));
    }
    if (headerCopy.getField(MIME.CONTENT_TYPE) == null) {
      final ContentType contentType;
      if (body instanceof AbstractContentBody) {
        contentType = ((AbstractContentBody) body).getContentType();
      } else {
        contentType = null;
      }
      if (contentType != null) {
        headerCopy.addField(new MinimalField(MIME.CONTENT_TYPE, contentType.toString()));
      } else {
        final StringBuilder buffer = new StringBuilder();
        buffer.append(this.body.getMimeType()); // MimeType cannot be null
        if (this.body.getCharset() != null) { // charset may legitimately be null
          buffer.append("; charset=");
          buffer.append(this.body.getCharset());
        }
        headerCopy.addField(new MinimalField(MIME.CONTENT_TYPE, buffer.toString()));
      }
    }
    if (headerCopy.getField(MIME.CONTENT_TRANSFER_ENC) == null) {
      // TE cannot be null
      headerCopy.addField(new MinimalField(MIME.CONTENT_TRANSFER_ENC, body.getTransferEncoding()));
    }
    return new FormBodyPart(this.name, this.body, headerCopy);
  }

  private static String encodeForHeader(final String headerName) {
    if (headerName == null) {
      return null;
    }
    final StringBuilder sb = new StringBuilder();
    for (int i = 0; i < headerName.length(); i++) {
      final char x = headerName.charAt(i);
      if (x == '"' || x == '\\' || x == '\r') {
        sb.append("\\");
      }
      sb.append(x);
    }
    return sb.toString();
  }

}
